W. Müller develops screen changer to enable sustainable use of recyclate

Germany-based blow moulding specialist W. Müller has developed a new generation of screen changers for its extruders in extrusion blow moulding. It is designed to be space-saving and suitable for installation in vertically oriented extruders.

A screen changer is recommended when using PCR, the experts at W. MÜLLER agree. Filtering the melt is also an essential element of controlled extrusion with these materials. The filtering screen consists of a fixed perforated carrier plate, which is covered by several interchangeable grids with different mesh sizes. If the differential pressure on this grid exceeds a certain value, the screen must be changed.

Managing Director Christian Müller said: "In the processing of recycled material, in particular PCR materials, the risk of contamination increases, which does not enter the production process from the outside but from the used material itself. These can be, for example, snippets of aluminium lids or sleeves of bottles. In operation, the screen is slowly getting clogged and must be changed regularly. How often, depends on the quality of the processed material. W. MÜLLER has designed its own system for this change."

The screen changer can be retrofitted and does not require any special safety precautions, as it does not have its own drive. It can be operated manually or by using a cordless screwdriver without effort.

For PCR processing, W. MÜLLER offers the ReCo3 system for its extrusion units, consisting of three independent extruders. The PCR layer is enclosed in the middle by two layers of virgin material. The extruders are mounted vertically for this process. Müller added: "Traditionally, there are no screen changers for such extruders, we are one of the very few suppliers on the market. Normally, the changers are too long to install vertically without risking the stability of the extruder."

W. MÜLLER constantly carries out tests with PCR and other recyclates in their in-house technical centres in Germany and the US in order to expand its expertise in this area.